GB2552225A

GB2552225A - A method of detecting that a particulate filter is clean from soot

Info

Publication number: GB2552225A
Application number: GB1612402.6A
Authority: GB
Inventors: Fritzche Jan; A Ramappan Vijay
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2016-07-14
Filing date: 2016-07-14
Publication date: 2018-01-17
Also published as: GB201612402D0

Abstract

A method of detecting that a particulate filter 280 of an internal combustion engine 100 is clean from soot, comprising: determining a value of a fuel quantity supplied into the internal combustion engine 110; determining a value of a temperature of the particulate filter 280; determining a value of an oxygen content in an exhaust gas discharged from the particulate filter 280; identifying that the particulate filter 280 is clean from soot, if the following concurrent conditions are met: the fuel quantity value is zero, the temperature value is equal to or larger than a predetermined threshold value thereof, and the oxygen content value is equal to a reference value of the oxygen content in an intake air. This method provides an alternative method of monitoring the level of particulate build-up in a particulate filter that may be performed when the engine is in a deceleration fuel cut-off condition, or over-run condition.

Description

(54) Title of the Invention: A method of detecting that a particulate filter is clean from soot Abstract Title: A method of detecting that a particulate filter is clean from soot (57) A method of detecting that a particulate filter 280 of an internal combustion engine 100 is clean from soot, comprising: determining a value of a fuel quantity supplied into the internal combustion engine 110; determining a value of a temperature of the particulate filter 280; determining a value of an oxygen content in an exhaust gas discharged from the particulate filter 280; identifying that the particulate filter 280 is clean from soot, if the following concurrent conditions are met: the fuel quantity value is zero, the temperature value is equal to or larger than a predetermined threshold value thereof, and the oxygen content value is equal to a reference value of the oxygen content in an intake air. This method provides an alternative method of monitoring the level of particulate build-up in a particulate filter that may be performed when the engine is in a deceleration fuel cut-off condition, or over-run condition.

FIG.l

1/2

140

FIG.2

145 □« p

2/2

S105

S120

Ο* t

FIG.4

A METHOD OF DETECTING THAT A PARTICULATE FILTER IS CLEAN FROM SOOT

TECHNICAL FIELD

The present disclosure generally relates to a particulate filter of an internal combustion engine, for example an internal combustior engine of a motor vehicle. More particularly, the present disclosure relates to a method of detecting whether the particulate filter is completely clean from particulate matter (soot).

BACKGROUND

It is known that an internal combustion engine, such as a diesel engine or a gasoline engine, may be provided with a particulate filter for trapping soot (e.g. impure carbon particles) that may be contained in the exhaust gasses.

When the amount of soot trapped inside the particulate filter exceeds a maximum admissible level, the particulate filter is cleaned up by means of a so-called regeneration procedure.

The regeneration procedure usually provides for increasing the particulate filter temperature up to a temperature that triggers the combustion of the trapped soot.

In order to properly manage the activation and the deactivation of the regeneration procedures, the amount of soot which is trapped inside the particulate filter (i.e. the so-called soot load) must be constantly monitored.

The known strategies for monitoring the soot load are based on measurements of the pressure differential across the particulate filter and/or on mathematical models configured to yield an estimation of the soot load on the basis of several different operating parameters.

However, a need exists for improving the estimation of the soot load and in particular for accurately determining if the particulate filter is completely clean from soot, for example at the end of a regeneration procedure.

SUMMARY

In view of the above, one of the objects of the present invention is that of providing a method that is able to accurately identify when the particulate filter is completely clean from soot.

This and other objects are achieved by the embodiments of the invention having the features recited in the independent claims. The dependent claims delineate additional aspects ofthe embodiments ofthe invention.

More particularly, an embodiment of the invention provides a method of detecting that a particulate filter of an internal combustion engine is clean from soot, comprising:

- determining a value of a fuel quantity supplied into the internal combustion engine (i.e. into the combustion chambers ofthe internal combustion engine),

- determining a value of a temperature of the particulate filter,

- determining a value of an oxygen content in an exhaust gas discharged from the particulate filter,

- identifying that the particulate filter is clean from soot, if the following concurrent conditions are met:

the fuel quantity value is zero, the particulate filter temperature value is equal to or larger than a predetermined threshold value thereof (e.g. a minimum value of the temperature of the particulate filter that is able to trigger a soot combustion), and the oxygen content value is equal to a reference value ofthe oxygen content in an intake air.

Thanks to this solution, the method is able to accurately identify when the particulate filter is completely clean from soot.

The method may be favorably implemented in conjunction with the known strategies for monitoring the soot load in the particulate filter (e.g. those based on the pressure differential across the particulate filter and/or on estimating models), for example in order to precisely determine a “starting condition” (i.e. clean filter) from which these strategies can start to calculate the soot load.

As a consequence, the strategies for monitoring the soot load may become more accurate as well as the entire management of the regeneration procedures, which imply the possibility of reducing fuel consumption and/or the risk of failures due to an overloaded particulate filter.

According to an aspect of the method, the particulate filter may be identified to be clean from soot provided that the above-mentioned concurrent conditions are fulfilled for longer than a predetermined period of time.

This aspect has the effect of improving the robustness of the method by reducing the risk of false “clean filter” identifications.

According to another aspect of the method, the oxygen content value in the exhaust gas may be determined by means of an oxygen sensor (also referred as to lambda sensor) located in an exhaust pipe downstream of the particulate filter, for example a wide range air fuel (WRAF) sensor.

Since an oxygen sensor is usually already provided in the exhaust pipe for other tasks, this aspect provides a very reliable solution for determining the oxygen content in the exhaust gas without requiring additional sensors.

According to the present disclosure, the method can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described above, and in the form of a computer program product comprising the computer program. The method can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.

Another embodiment of the invention provides an internal combustion engine comprising a particulate filter and an electronic control unit configured to:

- determine a value of a fuel quantity supplied into the internal combustion engine (i.e. into the combustion chambers of the internal combustion engine),

- determine a value of a temperature of the particulate filter,

- determine a value of an oxygen content in an exhaust gas discharged from the particulate filter,

- identify that the particulate filter is clean from soot, if all the following concurrent conditions are met:

the fuel quantity value is zero, the temperature value is equal to or larger than a predetermined threshold value thereof (e.g. a minimum value of the temperature of the particulate filter that is able to trigger a soot combustion), and the oxygen content value is equal to a reference value of the oxygen content in an intake air.

This embodiment of the invention basically achieves the same effects of the method above, in particular the effect of accurately identifying when the particulate filter is completely clean from soot.

The electronic control may further implement any of the additional aspects of the invention that have been described with reference to the method, in order to achieve the related effects. In particular, the electronic control unit may be configured to identify that the particulate filter is clean from soot provided that the conditions are fulfilled for longer than a predetermined time period. In addition, the electronic control unit may be configured to determine the oxygen content value in the exhaust gas by means of an oxygen sensor (also referred as to lambda sensor) located in an exhaust pipe downstream of the particulate filter, for example a wide range air fuel (WRAF) sensor.

Still another embodiment of the invention provides the use of an oxygen sensor (also referred as to lambda sensor) located in an exhaust pipe of an internal combustion engine for detecting that a particulate filter located in the exhaust pipe upstream of the oxygen sensor is clean from soot. Such an oxygen sensor may particularly be a wide range air fuel (WRAF) sensor.

As for the previously disclosed embodiments, this solution allows to accurately identify when the particulate filter is completely clean from soot, without requiring additional sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings.

Figure 1 schematically shows an automotive system.

Figure 2 shows an internal combustion engine of the automotive system according to the section A-A of figure 1.

Figure 3 is a flowchart of a detecting method according to an embodiment of the present disclosure.

Figure 4 is a diagram that represents the variation of the particulate filter temperature (curve A) and of the oxygen concentration in the exhaust gas discharged by the particulate filter (curve B) over time.

DETAILED DESCRIPTION

Some embodiments may include an automotive system 100, as shown in figures 1 and 2, that includes an internal combustion engine (ICE) 110. In the instant example, the ICE 110 is a compression-ignition engine (e.g. Diesel engine), but in other embodiments it may be a spark-ignition engine (e.g. gasoline engine). The ICE 110 has an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movement of the piston 140.

The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received from a fuel source 190. Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gasses to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold

200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gasses from an exhaust manifold 225 that directs exhaust gasses from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gasses through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust gasses exit the turbine 250 and are directed into an exhaust system 270. The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices. The aftertreatment devices may be any device configured to change the composition of the exhaust gasses. In the present example, the aftertreatment devices include at least one particulate filter 280, which is provided for trapping particulate matter (soot) contained in the exhaust gasses. The aftertreatment devices may also include an oxidization catalyst 285 located in the exhaust pipe 275 upstream of the particulate filter 280, as well as other devices such as catalytic converters (two and three way), lean NOx traps, hydrocarbon adsorbers and selective catalytic reduction (SCR) systems. As an alternative, the oxidization catalyst 285 may be located in the exhaust pipe 275 either downstream of the particulate filter 280 or combined with the particulate filter 280 (this combination is usually used for gasoline engine and it is referred as to 4-way gasoline particulate filter). Other embodiments may include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gasses in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gasses in the EGR system 300.

The automotive system 100 may further include an electronic control unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110. The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445. The sensors may also include an oxygen sensor 435 (also referred as to lambda sensor), for example a wide range air fuel (WRAF) sensor, located in the exhaust pipe 275 downstream of the particulate filter 280 to measure the oxygen content (or equivalently a so-called “lambda” parameter) in the exhaust gasses that exit the particulate filter 280. Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, and the cam phaser 155. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with a memory system and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system 460, and send and receive signals to/from the interface bus. The memory system 460 may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors and control devices. The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.

The program stored in the memory system 460 is transmitted from outside via a cable or in a wireless fashion. Outside the automotive system 100 it is normally visible as a computer program product, which is also called computer readable medium or machine readable medium in the art, and which should be understood to be a computer program code residing on a carrier, said carrier being transitory or non-transitory in nature with the consequence that the computer program product can be regarded to be transitory or nontransitory in nature.

An example of a transitory computer program product is a signal, e.g. an electromagnetic signal such as an optical signal, which is a transitory carrier for the computer program code. Carrying such computer program code can be achieved by modulating the signal by a conventional modulation technique such as QPSK for digital data, such that binary data representing said computer program code is impressed on the transitory electromagnetic signal. Such signals are e.g. made use of when transmitting computer program code in a wireless fashion via a wireless connection to a laptop.

In case of a non-transitory computer program product the computer program code is embodied in a tangible storage medium. The storage medium is then the non-transitory carrier mentioned above, such that the computer program code is permanently or non-permanently stored in a retrievable way in or on this storage medium. The storage medium can be of conventional type known in computer technology such as a flash memory, an Asic, a CD or the like.

Instead of an ECU 450, the automotive system 100 may have a different type of processor to provide the electronic logic, e.g. an embedded controller, an onboard computer, or any processing module that might be deployed in the vehicle.

During the operation of the ICE 110, the soot produced by the combustion of the fuel inside the combustion chamber 150 is discharged with the exhaust gasses and progressively accumulated inside the particulate filter 280.

When the amount of soot trapped inside the particulate filter 280 exceeds a maximum admissible level, the ECU 450 may activate a so-called regeneration procedure, which generally provides for increasing the temperature of the particulate filter 280 up to a value that triggers the combustion of the trapped soot.

In order to properly manage the activation and the deactivation of the regeneration procedure, the ECU 450 may be configured to monitor the amount of soot which is trapped inside the particulate filter (i.e. the soot load).

Known strategies to monitor the soot load are based on a measurement of the pressure differential across the particulate filter and/or on a mathematical model configured to yield an estimation of the soot load based on several different engine operating parameters. However, in order that these strategies provide accurate results, the ECU 450 should be able to precisely determine when the particulate filter 280 is completely clean from soot, for example at the end of a regeneration procedure.

To this task, the ECU 450 may favorably use the oxygen sensor 435 which is located in the exhaust pipe 275 downstream of the particulate filter 280.

More particularly, the ECU may carry out the detecting method represented in the flow chart of figure 3.

One of the steps of such method provides for the ECU 450 to determine (block S100) a current value Q of a fuel quantity supplied by the fuel injectors 160 into the ICE 110, namely into the combustion chamber 150.

This fuel quantity value Q may be determined by the ECU 450 according to conventional strategies and generally on the basis of several operating parameters, including but not limited to, the position of the accelerator pedal as measured by the accelerator pedal position sensor 445.

The method further provides for the ECU 450 to determine (block S105) a current value T of a temperature of the particulate filter 280.

This temperature value T may be determined by the ECU 450 using a dedicated sensor (not shown) or estimated on the basis of other parameters, for example on the basis of the temperature of the exhaust gasses as measured by the exhaust temperature sensors 430. The method further provides for the ECU 450 to determine (block S110) a current value O of an oxygen content in the exhaust gasses that are discharged from the particulate filter 280, for example by means of the oxygen sensor 435.

The oxygen content may be expressed in term of a volumetric percentage of oxygen in the exhaust gasses or in term of any other parameter (for example a lambda parameter) that represents the oxygen content.

At this point, the ECU 450 may be configured to check (block S115) if three concurrent conditions are fulfilled at the same time.

A first condition is that the fuel quantity value Q is zero, which means that no fuel is currently supplied into the combustion chamber 150 of the ICE 110, for example because the ICE 110 is currently operating under a so-called deceleration fuel cut-off (DFCO) condition. A second condition is that the temperature value T of the particulate filter 280 is equal to or larger than a predetermined threshold value thereof, namely a minimum value Tmin of the temperature that is able to trigger a soot combustion inside the particulate filter 280.

In other words, if the particulate filter temperature is equal to or larger than the minimum value Tmin, the soot accumulated in the particulate filter 280 burns off. If conversely the particulate filter temperature is smaller than the minimum value Tmin, the soot accumulated in the particulate filter 280 remain unburnt.

The minimum value T_min of the particulate filter temperature may be a calibration value which is pre-determined by means of an experimental activity and then stored in the memory system 460 connected to the ECU 450. Generally speaking, the minimum value Tmin of the particulate filter temperature may be of about 550°C.

The third condition is that the oxygen content value O in the exhaust gasses is equal to a reference value O* of the oxygen content in an intake air.

As a matter of fact, the oxygen content O* of the intake air is the oxygen content of the ambient air of the environment where the ICE 110 operates. This reference value O* may be measured by the ECU 450 with a dedicated sensor or simply assumed as a calibration parameter. Indeed, the oxygen content reference value O* of the intake air is constant or almost constant and it generally corresponds to a value of about 21 % of the whole volume of the intake air.

If all the three concurrent conditions are fulfilled at the same time, then the ECU 450 may be finally configured to identify (block S120) that the particulate filter 280 is completely clean from soot.

In some embodiments, the three conditions may checked more than once and the ECU 450 may be configured to identify that the particulate filter 280 is completely clean of soot, only if the three conditions are constantly or concurrently fulfilled for longer than a predetermined time period, for example for longer than 5 seconds.

This detecting method can be understood considering that the oxygen content of the exhaust gas exiting the particulate filter 280 generally corresponds to the oxygen content of the intake air minus the oxygen quantity spent for the fuel combustion inside the combustion chamber 150 of the ICE 110 and the oxygen quantity spent for the soot combustion inside the particulate filter 280.

When no fuel is supplied into the combustion chamber 150 (first condition), for example because the ICE 110 is operating under a DFCO condition, there is no fuel combustion inside the combustion chamber 150 (or in any other part of the exhaust system 270 upstream of the particulate filter 280). Under such a condition, the oxygen content of the exhaust gas discharged from the particulate filter 280 may only be affected by the soot combustion that may be triggered by the particulate filter temperature exceeding the minimum value T_min (second condition). However, the fact that the oxygen content of the exhaust gas discharged from the particulate filter 280 is equal to the oxygen content of the intake air (third condition) implies that no soot combustion is actually occurring in the particulate filter 280, despite the favorable thermal (second) condition, and thus that no soot is present inside the particulate filter 280.

The validity of these considerations has been also confirmed by experimental activities as shown in the diagram of figure 4, wherein the curve A indicates the temperature of a particulate filter 280, the curve B indicated the oxygen concentration in the exhaust gasses discharged from the particulate filter 280, and the time instant t indicated the beginning of a phase in which the ICE 110 is operated under a DFCO condition.

This diagram clearly shows that, while the particulate filter temperature is above the minimum value Tmin thereof, upon the beginning of the DFCO phase, the oxygen content in the exhaust gas rapidly increases and, after the end of a phase of soot regeneration in which the oxygen oscillates (see the portion of the curve B within the ellipse C), stabilizes at the value O* corresponding to the oxygen concentration in the intake air (see the portion of the curve B within the ellipse D).

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFERENCES

100 automotive system 110 internal combustion engine

120 engine block

125 cylinder

130 cylinder head

135 camshaft

140 piston

145 crankshaft

150 combustion chamber

155 cam phaser

160 fuel injector

170 fuel rail

180 fuel pump

190 fuel source

200 intake manifold

205 air intake duct

210 intake port

215 valves

220 exhaust port

225 exhaust manifold

230 turbocharger

240 compressor

250 turbine

260 intercooler

270 exhaust system

275 exhaust pipe

280 particulate filter

285 oxidization catalyst

290 VGT actuator

300 exhaust gas recirculation system 310 EGR cooler

320 EGR valve

330 throttle body

340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 combustion pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor

410 cam position sensor

420 crank position sensor

430 exhaust pressure and temperature sensors

435 oxygen sensor

440 EGR temperature sensor

445 accelerator pedal position sensor

450 ECU

460 memory system

S100 block

S105 block

S110 block

S115 block

A curve

B curve

C ellipse

D ellipse

Claims

1. A method of detecting that a particulate filter (280) of an internal combustion engine (100) is clean from soot, comprising:

- determining a value of a fuel quantity supplied into the internal combustion engine (110),

- determining a value of a temperature of the particulate filter (280),

- determining a value of an oxygen content in an exhaust gas discharged from the particulate filter (280),

- identifying that the particulate filter (280) is clean from soot, if the following concurrent conditions are met:

the fuel quantity value is zero, the temperature value is equal to or larger than a predetermined threshold value thereof, and the oxygen content value is equal to a reference value of the oxygen content in an intake air.

2. A method according to claim 1, wherein the particulate filter (280) is identified to be clean from soot provided that the concurrent conditions are fulfilled for longer than a predetermined time period.

3. A method according to any of the preceding claims, wherein the oxygen content value in the exhaust gas is determined by means of an oxygen sensor (435) located in an exhaust pipe (275) downstream of the particulate filter (280).

4. A computer program comprising a program-code for carrying out the method according to any of the preceding claims

5. A computer program product comprising the computer program according to claim

4.

6. An electromagnetic signal modulated to carry a sequence of data bits which represent a computer program according to claim 4.

7. An internal combustion engine (110) comprising a particulate filter (280) and an electronic control unit (450) configured to:

- determine a value of a fuel quantity supplied into the internal combustion engine (110),

- determine a value of a temperature of the particulate filter (280),

- determine a value of an oxygen content in an exhaust gas discharged from the particulate filter (280),

- identify that the particulate filter (280) is clean from soot, if all the following concurrent conditions are met:

the fuel quantity value is zero, the temperature value is equal to or larger than a predetermined threshold value thereof, and the oxygen content value is equal to a reference value ofthe oxygen content in an intake air.

8. An internal combustion engine (110) according to claim 7, wherein the electronic control unit (450) is configured to identify that the particulate filter is clean from soot provided that the concurrent conditions are fulfilled for longer than a predetermined time period.

9. An internal combustion engine according to claim 7 or 8, wherein the electronic control unit (450) is configured to determine the oxygen content value in the exhaust gas by means of an oxygen sensor (435) located in an exhaust pipe (275) downstream of the particulate filter (280).

10. Use of an oxygen sensor (435) located in an exhaust pipe (275) of an internal combustion engine (110) for detecting that particulate filter (280) located in the exhaust pipe (275) upstream of the oxygen sensor (435) is clean from soot.

Intellectual

Property

Office

Application No: GB1612402.6 Examiner: Bryce D'Souza